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P H O T O G R A P H Y C O N T E S T Sponsored by A.J. Hirsch |
Elzbieta Muir
Second Place
2005 OAPT Members Photo Contest
Serendipity
While driving down the mountainous road to Delphi in Greece I stopped to take a photograph of a picturesque view of the hills (photo #1). While admiring the scenery, I exclaimed: “There is a rainbow there!”, the rainbow I have not seen through the lens of my camera just a moment ago. Rotate the polarizer, I realized, and there it was: the colourful rainbow! (photo #2).
Light from the sun is unpolarized. Sunlight that came from behind me was refracted into the water droplets of the rainbow in front of me, reflected from the back surface of the droplet, refracted again upon exiting the droplet and travelled to my camera. Unpolarized light is polarized upon reflection from the surface of water. For most angles of incidence, waves for which the electric field vector E is perpendicular to the plane of incidence (the plane of incidence is the plane containing the incident and reflected rays and the normal to the surface), are reflected more strongly than those for which E lies in this plane. Thus, the reflected light is predominantly polarized parallel to the reflecting surface, in this case the plane of the rainbow. By rotating the polarizing filter in my camera I aligned the polarizing axis of the filter with the direction of polarization of light coming from the rainbow and the bow was clearly visible. Rotating the filter 90 degrees essentially eliminated the rainbow when looking through the lens of the camera.
The point from which the photograph with the rainbow was taken was shifted slightly from that of the other photograph for dramatic effect, i.e., to have the rainbow appear to be springing from the road sign.